Compliance activated multi-diaphragm



COMPLIANCE ACTIVATED MULT I,DIAPHRAGM Filed June 22, 1966 lo 48 44 46H65 2o- 4s s4 lo-- 1 FIGS INVENTOR BRUNO G. STAFFEN o 200 500 I000 20005990 IOOOO 20000 BY QW/M ATTORNEYS United States Patent 3 342,286COMPLIANCE ACTIVATED MULTI-DIAPI-IRAGM Bruno G. Staffen, Chicago, Ill.,assignor to Motorola, Inc., Franklin Park, Ill., a corporation ofIllinois Filed June 22, 1966, Ser. No. 559,600 6 Claims. (Cl. 181-32)This invention relates to diaphragms, especially those to be used inaudio transducers, such as a speaker, and more particularly todiaphragms capable of having multi- Inode vibrations.

In providing speakers for automobile radios, for example, volumetricrequirements are quite important. For meeting such requirements it isdesired to provide a speaker diaphragm which has a high aspect ratio andadditionally is shallow as measured from the outer edge of the diaphragmto the driving means. In speakers, and other audio transducers havingdiaphragms, the aspect ratio is the ratio of the diaphragm major axis toits minor axis.

It has been found that in providing speakers having high aspect ratioslocalized modal vibrations are set up within the diaphragm along themajor axis resulting in greatly decreased speaker output. The diaphragmis incoherently flapping rather than vibrating to produce sound.Diaphragms are particularly susceptible to such undesired vibrations atthe middle to higher audio frequencies, i.e. above 1000 c.p.s.

Attempts to obivate the above described problem include providing aplurality of spaced-apart corrugations in the speaker diaphragm. Some ofsuch corrugations were made concentric with respect to each other, whileothers not being perfectly concentric maintained the same aspect ratioof the speaker diaphragm. While improving speaker operations suchcorrugations did not satisfactorily prevent decreased speaker output inthe middle to higher frequencies, especially in those speakers having alow profile. Such diaphragms had sharply varying amplitude responses asthe frequency was increased, i.e. so called peaks and valleys inamplitude output response curves measured against frequency.

Therefore, it is an object of this invention to provide a diaphragm foran audio transducer having a high aspect ratio but which operates in amulti-piston mode for providing improved middle-to-high frequencyresponse.

It is another object of this invention to provide a lowprofile diaphragmexhibiting smooth response in the middle-to-higher audio frequencies.

According to this invention a unitary diaphragm is formed to providesubstantially independent piston areas each having different aspectratios and resonant frequencies, such that the coaction between thevarious piston areas and compliance corrugations smooth and improve themiddle-to-high frequency response of the diaphragm.

Referring now to the accompanying drawing:

FIG. 1 is a plan view of a preferred embodiment of the presentinvention;

FIG. 2 is a partial sectional view of the FIG. 1 preferred embodiment astaken in the direction of the arrows along line 2-2;

FIG. 3 is a partial sectional view of the FIG. 1 embodiment taken in thedirection of the arrows along line 33 and which shows a cross-section ofthe preferred embodiment along its minor axis;

FIG. 4 is a partial-sectional view of the FIG. 1 embodiment taken in thedirection of the arrows along line 4-4 showing the cross-sectionalcharacteristics along the major axis, and being approximately the actualsize of a diaphragm constructed embodying this invention.

FIG. 5 is a graph illustrating frequency response of the FIG. 1preferred embodiment and another speaker having the same dimensions butnot using the invention; and

FIGS. 6, 7 and 8 are schematic illustrations of alternate embodiments ofthis invention.

A diaphragm having a high aspect ratio is provided with a plurality ofsets of compliant corrugations, some of which cross the major axis in amajor piston area. Such crossings provide a second diaphragm portionwhich acts as an inner piston area and has a different aspect ratio thanthe diaphragm. The major-axis crossing corrugations effectively anddynamically decouple the second piston area from the major or outerpiston area. Both the inner and outer piston areas preferably have thesame minor axis.

Referring now more particularly to FIGS. 1-4, inclusive, like numeralsindicate like parts and structural features of the illustrated preferredembodiment. The diaphragm 10 consists of pliant paper press-formed or anaqueous slurry deposited on a forming mold formed to the illustratedshape. Diaphragm 10 may be mounted along its outer edges 10F on a frame(not shown) in the usual manner. A voice coil or otherelectro-mechanical transducers may be affixed to diaphragm 10* adjacentits aperture 10A. Inwardly of outer edge 10F are formed a pair of outercompliant corrugations 12 and 14. A third and innermost outer compliantcorrugation is formed by a lift hand portion corrugation 16, a righthand portion corrugation 18 and intermediate corrugation portions 20.Even though the corrugation portions are discontinuous, the fourportions cooperate to provide action substantially similar to acontinuous corrugation. It is well known that the entire diaphragm 10will flex between major corrugation 12 and outer edge 10F for providinga first resonant frequency of diaphragm 10.

Inner or minor compliance corrugations are formed by the combination ofportions 20, which also form a part of the outer or major corrugation16-18-20, are combined with corrugation portions 22 to form a minorcompliance corrugation 20-22. A second inner or minor corrugation isformed by a left hand portion 24, a right hand portion 25 in combinationwith corrugation portions 26 of continuous major corrugation 14.

It should be noted that corrugation portions 24 and 26 are discontinuousin the same manner that portions 20 are discontinuous from outercorrugation portions 16 and 18. Such discontinuities do not prevent thedescribed affected corrugation portions from coacting similar to asingle continuous corrugation. Therefore, such minor and majorcorrugations are effectively merged over a part of their respectiveextents.

The above described compliance corrugations provide, in addition to amajor piston area consisting of the entire area inside majorcorrugations 12, 14, and 1648-20, a minor piston area 28 inside theminor compliance corrugations 20-22 and 24-26 plus the two intermediatepiston areas 30 between the corrugation portions 16 and 24 at oppositeend portions of diaphragm 10.

Expressed in another way, the major piston area is defined bycorrugations 12, 14, 16 and 18 and the minor piston area is defined bycorrugations 22, 24 and 25. Along line 33, the corrugations merge sothat corrugations 16 and 18 are discontinuous from one another andsimilarly corrugations 24 and 25 are discontinuous.

The described compliance corrugations also dynamically de-couple minorpiston area 28 from the major piston area which is the area withincorrugations 12, 14 and 16-1820 to provide an additional resonantfrequency by piston area 30 and the minor corrugations. In theillustrated embodiment such effective decoupling is especiallynoticeable at frequencies above 1,000 cycles per second. Additionallythe described intermediate piston areas 30 are effectively decoupledfrom both the minor and major piston areas, so that they haveindependent resonant frequencies.

Diaphragm 10 major axis is along line 44 while its minor axis is alongline 33. The major axis length is determined by the outer or majorcompliance corrugations 12, 14 and 16-18-20. Minor piston area 28 hasits major and minor axes also disposed along said lines. The minor axesalong line 3-3 have the same length for both the minor and major pistonareas. The minor piston area 28 major axis is much shorter than thediaphragm major axis, in that its length is determined by minorcompliance corrugations 20-22. From inspection of FIG. 1 it is clearlyseen that the aspect ratio of the minor piston area 28 is much smallerthan that of major piston area inside the major compliance corrugations12, 14, and 16-18-20. As such, piston area 28 is more eflicient in themiddle-to-higher frequency range.

The diaphragm along major axis 44 is also stiffened by minor compliancecorrugations 20-22, 24-26 extending across the major axis. In additionto providing above described action such corrugations also serve toinhibit undesired modal vibrations along the major axis.

The profile of diaphragm 10 is quite shallow in that the diaphragmlength along line 44 is substantially greater than the diaphragm depthindicated by line 39.

Referring now to FIG. 5, curve 40 shows the frequency response of aspeaker having the dimensions shown in FIG. 1, but without minorcorrugations 20-22, 24-26, additional piston areas 28 and 30, and theinnermost major corrugations 16-18-20 was made continuous. Curve 40illustrates the frequency response of a FIG. 1 embodiment as used in aspeaker. It should be noted that the middle-tohigher frequency response,i.e. above 1,000 cycles, is smoothed in the FIG. 1 embodiment whereinthe aspect ratios of various piston areas are different with respect toeach other. Also the peak response at 800 c.p.s. is smoothed by the FIG.1 diaphragm. The narrow clips at 2.5 and 5.0 kc. in curve 40 arecritical phasing acoustic effects which are swamped out when radiationis averaged over various angles with respect to the diaphragm axis ofvibration.

The frequency response of the FIG. 1 embodiment may be altered byvarying the density of the diaphragm in the various piston areas. Thiscan be easily done when the diaphragm is manufactured by pressingcompliant paper. For example, piston area 28 may be pressed very hard tomake it quite dense, while piston areas 30 may be formed under lesspressure and therefore be less dense. Making piston area 30 less densereduces the sharpness in the upper frequency amplitude response cutoff,tending to smooth the middle frequency response of the diaphragm.

Referring now to FIGS. 6, 7 and 8 the lines therein schematicallyrepresent sets of compliance corrugations, such as those illustrated inthe FIG. 1 embodiment. Aperture 48 is provided in all FIGS. 6-8 forreceiving a driving coil or other audio transducer suitable for use witha diaphragm. In FIG. 6 there is illustrated in outer or major compliancecorrugation set 44 in the shape of an elipse and with an inner or minorset of circular corrugations 46. In FIG. 7 the outer corrugation set 50is circular while the minor corrugation set 52 is elliptical. In thislatter modification the major axis 51 is the same for both compliancecorrugation sets 50 and 52, while the horizontal minor axes along line53 are different for corrugations 50 and 52. This difference providesdifferent aspect ratios. In FIG. 8, line 54 represents an outercorrugation set having a somewhat elliptical form while corrugation set56 is circular. Note in this particular embodiment the aperture 48 isnot centered with respect to one set of corrugations. Yet otherconfigurations of multi-piston diaphragms may be formed, an importantfeature being different aspect ratios of the minor and major pistonareas.

It is understood that the described diaphragm in addition to being usedin a speaker may also be used in a microphone type of transducer.

What is claimed is:

1. A unitary diaphragm including: an outer set of cOmpliancecorrugations the area within which defines a major piston area, an innerset of compliance corrugations formed within said outer set and mergingwith a limited portion thereof, the area within said inner set defininga minor piston area, at least one intermediate piston area between saidinner and outer sets of compliance corrugations, said minor piston areabeing entirely surrounded by said inner set of compliance corrugationsso that it is dynamically decoupled from said major and intermediatepiston areas, whereby each of said piston areas has an independentresonant frequency.

2.. The diaphragm of claim 1 wherein said major and minor piston areaseach have a first and a second axis, said first axis of each of saidmajor and minor piston areas being coincident with one another, saidsecond axis of said major piston area being aligned with and having alength longer than the length of said second axis of said minor pistonarea.

3. The diaphragm of claim 2 having a depth dimension relatively shortwith respect to the length of said second axis of said major pistonarea.

4. An elliptically shaped unitary diaphragm including: an ellipticallyshaped outer set of compliance corrugations the area within whichdefines a major piston area having an elliptical shape, an ellipticallyshaped inner set of compliance corrugations formed within said outer setand merging with a limited portion thereof, the area Within said innerset defining a minor piston area having an elliptical shape, said majorand minor piston areas each having a major and a minor axis, said minoraxis of each of said piston areas being coincident with one another,said major axis of said major piston area being aligned with and havinga length longer than the length of said major axis of said minor pistonarea, and two intermediate piston areas formed between said inner andouter sets of compliance corrugations at respective end portions of saidmajor axis of said major piston area, said minor piston area beingentirely surrounded by said inner set of compliance corrugations so thatit is dynamically decoupled from said major and intermediate pistonareas, whereby said piston areas have independent resonant frequencies.

5. The diaphragm of claim 4 having a depth dimension relatively shortwith respect to the length of said major axis of said major piston area.

6. The diaphragm of claim 4 with said minor piston area and saidintermediate piston areas having different densities.

References Cited UNITED STATES PATENTS 1,872,081 8/1932 Hawley 181-322,358,823 9/1944 OConnor et al 18131 2,549,139 4/ 1951 Stevens 181-322,834,424 5/1958 Badmaieff 18132 2,845,135 7/1958 Cohen et al 181312,890,760 6/1959 Bobb 18131 2,962,109 11/ 1960 Haerther 18132 3,095,9417/1963 Hassan 18132 3,111,189 11/1963 Scholl 181-32 3,166,148 1/1965Tibbetts 181-32 3,180,945 4/ 1965 Suzuki 1791 15 STEPHEN I. TOMSKY,Primary Examiner.

1. A UNITARY DIAPHRAGM INCLUDING: AN OUTER SET OF COMPLIANCE CORRUGATIONS THE AREA WITHIN WHICH DEFINES A MAJOR PISTON AREA, AN INNER SET OF COMPLIANCE CORRUGATIONS FORMED WITHIN SAID OUTER SET AND MERGING WITH A LIMITED PORTION THEREOF, THE AREA WITHIN SAID INNER SET DEFINING A MINOR PISTON AREA, AT LEAST ONE INTERMEDIATE PISTON AREA BETWEEN SAID INNER AND OUTER SETS OF COMPLIANCE CORRUGATIONS, SAID MINOR PISTON AREA BEING ENTIRELY SURROUNDED BY SAID INNER SET OF COMPLIANCE CORRUGATONS SO THAT IT IS DYNAMICALLY DECOUPLED FROM SAID MAJOR AND INTERMEDIATE PISTON AREAS, WHEREBY EACH OF SAID PISTON AREAS HAS AN INDEPENDENT RESONANT FREQUENCY. 